The present invention relates to a catalytic converter for exhaust gas purification employed in an automotive vehicle internal combustion engine, and more particularly to an apparatus for warming up of the catalyst in the converter.
Conventional automotive vehicle engines are provided with a catalytic converter in the exhaust passageway. The converter efficiency is low when the temperature of the catalyst is low. Thus spark timing is retarded to increase the exhaust temperature, thereby warming up the catalyst sufficiently. For example, in a conventional automotive vehicle engine, intake vacuum is conducted from a vacuum inlet near the throttle valve in the air intake passageway through a vacuum passageway to a vacuum advance mechanism of the distributor. On the other hand, an atmospheric air introduction passageway is provided so as to communicate with an intermediate point in the vacuum passageway, and has a bimetallic valve responsive to the temperature of engine coolant. The bimetallic valve deforms to open the atmospheric air introduction passageway and introduce atmospheric air into the vacuum advance mechanism to retard the spark timing when the temperature of the coolant is relatively low, whereas the bimetallic valve deforms to close the atmospheric air introduction passageway when the temperature of the cooling water is relatively high.
However, this warm-up function has previously been effected dependent on the coolant temperature of the engine, and has had nothing to do with the actual state of the catalytic converter. Thus, the conventional apparatus has the following drawbacks:
(1) Even if the catalytic converter is already warmed up, spark timing may be unnecessarily retarded and as a result, fuel will be consumed uselessly; and
(2) During extended vehicle operation at low speeds, the catalyst may be insufficiently warm so that harmful exhaust emissions will be produced even though the temperature of the coolant is sufficient to prevent retardation of spark timing.